(AP) -- Danica Patrick wrecked just minutes into what turned into a dicey first practice session Friday at Bristol Motor Speedway.

In all, four drivers had to go to backup cars before the halfway mark of the 90-minute session, including 15-time Bristol winner Kyle Busch.

Denny Hamlin, who watched the first 15 minutes of practice from pit road, attributed the wrecks to drivers adapting to NASCAR's new aerodynamic rules and Goodyear's tire compound producing faster speeds.

"I really don't think it's treacherous," Hamlin told Fox Sports 1. "It's just the speeds are so much higher than we've seen. It takes a little getting used to. We are all out there fighting for a tenth-of-a-second, a hundredth-of-a-second at Bristol. I think it comes more from us pushing the edge than it is treacherous."

Patrick was the first to wreck, losing control roughly three minutes into the session. She slammed into Parker Kligerman's car, and his Swan Racing team appeared to be trying to fix his Toyota as Stewart-Haas Racing immediately pulled out the backup Chevrolet for Patrick.

Justin Allgaier then hit the wall, then Busch. Moments later, Greg Biffle crashed. All three went to backup cars.

Ricky Stenhouse Jr. later scraped the wall, but didn't appear to do much damage.

Ryan Newman, who missed the first 15 minutes of practice because of a penalty last week at Las Vegas, found the beginning of practice entertaining.

"We sat there and watched a few guys crash," he said. "It seems like the cars are really, really sensitive to some changes just because the cars are so stiff now because of the rigidity of how we're running them. Once you lose it, you really lose it, which is what we've seen."

Kenseth to use standby drivers at California

Matt Kenseth has a contingency plan for next week's race at California as he awaits the birth of his third child.

Sam Hornish Jr. will be on standby for the Nationwide Series race at Auto Club Speedway, and Jeff Burton will be in place in case Kenseth needs a replacement driver for the Sprint Cup race.

"Although Jeff Burton is not crazy about going to the West Coast, he agreed to standby to practice or something if we needed that for a session," Kenseth said.

Burton, who is running a limited schedule this season, tweeted Friday: "Friends don't let friends drive with baby on the way."

Kenseth has not said exactly when Katie Kenseth is due, but he joked several times that he has told her to have the baby girl on a Monday or Tuesday when he's not busy with his duties as a Joe Gibbs Racing driver.

Page 2 of 2 - With rain expected to impact Sunday's race at Bristol Motor Speedway, he joked that Monday of next week is now off the table as a potential due date.

"If it rains Sunday, she was praying for Monday, so we had to change that to Tuesday if it's going to be this week," Kenseth said Friday.

He paused when he learned there may be bad weather in Bristol on Monday, too.

"Oh, it's supposed to snow Monday?" he asked. "So I guess if we can't race then we can still have her on Monday."

Kenseth does not have standby drivers for this weekend at Bristol, where he's scheduled to run both the Nationwide and Cup races.

Meanwhile, Paul Menard has Truck Series champion Matt Crafton on standby for a second consecutive week.

Menard's wife, Jennifer, is expecting their first child in North Carolina, and Crafton was on standby last weekend in Las Vegas. He wasn't needed as Menard finished a season-best third.